//
// TextSourceVersionProvider.cs
//
// Taken from NRefactory 5.
//
// Author:
//       Mike Krüger <mkrueger@xamarin.com>
//
// Copyright (c) 2014 Xamarin Inc. (http://xamarin.com)
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
using System;
using System.Collections.Generic;
using System.Linq;

namespace MonoDevelop.Core.Text
{
	/// <summary>
	/// Provides ITextSourceVersion instances.
	/// </summary>
	[Obsolete ("Use the Microsoft.VisualStudio.Text APIs")] 
	public class TextSourceVersionProvider
	{
		Version currentVersion;

		public TextSourceVersionProvider ()
		{
			this.currentVersion = new Version (this);
		}

		/// <summary>
		/// Gets the current version.
		/// </summary>
		public ITextSourceVersion CurrentVersion {
			get { return currentVersion; }
		}

		/// <summary>
		/// Replaces the current version with a new version.
		/// </summary>
		/// <param name="change">Change from current version to new version</param>
		public void AppendChange (TextChangeEventArgs change)
		{
			if (change == null)
				throw new ArgumentNullException ("change");
			currentVersion.change = change;
			currentVersion.next = new Version (currentVersion);
			currentVersion = currentVersion.next;
		}

		sealed class Version : ITextSourceVersion
		{

			// Reference back to the provider.
			// Used to determine if two checkpoints belong to the same document.
			readonly TextSourceVersionProvider provider;
			// ID used for CompareAge()
			readonly int id;

			// the change from this version to the next version
			internal TextChangeEventArgs change;
			internal Version next;

			internal Version (TextSourceVersionProvider provider)
			{
				this.provider = provider;
			}

			internal Version (Version prev)
			{
				this.provider = prev.provider;
				this.id = unchecked(prev.id + 1);
			}

			public bool BelongsToSameDocumentAs (ITextSourceVersion other)
			{
				Version o = other as Version;
				return o != null && provider == o.provider;
			}

			public int CompareAge (ITextSourceVersion other)
			{
				if (other == null)
					throw new ArgumentNullException ("other");
				var o = other as Version;
				if (o == null || provider != o.provider)
					throw new ArgumentException ("Versions do not belong to the same document.");
				// We will allow overflows, but assume that the maximum distance between checkpoints is 2^31-1.
				// This is guaranteed on x86 because so many checkpoints don't fit into memory.
				return Math.Sign (unchecked(this.id - o.id));
			}

			public IEnumerable<TextChangeEventArgs> GetChangesTo (ITextSourceVersion other)
			{
				int result = CompareAge (other);
				Version o = (Version)other;
				if (result < 0)
					return GetForwardChanges (o);
				else if (result > 0)
					return o.GetForwardChanges (this).Reverse ().Select (change => change.Invert ());
				return Enumerable.Empty<TextChangeEventArgs> ();
			}

			IEnumerable<TextChangeEventArgs> GetForwardChanges (Version other)
			{
				for (Version node = this; node != other; node = node.next) {
					yield return node.change;
				}
			}

			public int MoveOffsetTo (ITextSourceVersion other, int oldOffset)
			{
				int offset = oldOffset;
				foreach (var e in GetChangesTo(other)) {
					offset = e.GetNewOffset (offset);
				}
				return offset;
			}
		}
	}
}